It is planned to develop and refine the use of a small, ophthalmic B-scan ultrasound probe to accurately localize the position of stones in the kidney at operation. It is planned to design a device to fit on the probe head to mark the position of the stone to effect its removal. It will also be necessary to accurately describe the ultrasound architecture of both normal and diseased kidneys. This will aid the surgeon in distinguishing calculi from areas of fibrosis and portions of the normal calyceal architecture which also produce similar strong echos. It is planned to develop an atlas relating the ultrasound image to the familiar anatomic cross-section of the kidney and to establish a training method for surgeons to use this instrument. The successful development of such an instrument should greatly decrease the morbidity of nephrolithotomy and improve the results by decreasing the incidence of recurrent stone formation and facilitating the control of post-operative infection.